Q13E - Organic Chemistry (Mcmurry)

Question

How would you prepare the following carbonyl compounds from a nitrile?

Step-by-Step Solution

Answer

(a)

The given carbonyl compound (3-pentanone) is prepared from propanenitrile as shown below:

(b)

The target carbonyl compound (p-nitroacetophenone) is prepared from 4-nitrobenzonitrile as shown below:

Step 1: Preparation of 3-pentanone from the respective nitrile.

The target compound, 3-pentanone is a symmetrical ketone that would be prepared by the Grignard reaction of ethyl magnesium bromide with propane nitrile through an intermediate imine anion. 

The addition of aqueous acid to the imine salt to produce the final product as shown below:

Step 2: Preparation of p-nitroacetophenone from 4-nitrobenzonitrile.

The desired carbonyl compound, p-nitro acetophenone would be prepared from 4-nitrobenzonitrile as a starting material. 

The starting material is treated with Grignard reagent, methyl magnesium bromide to generate an intermediate imine anion (unstable). 

The acidic hydrolysis of this imine anion gives p-nitro acetophenone as shown below: